Block initialize

canvas.rb

@@ -0,0 +1,26 @@
+class Canvas
+  attr_accessor :width, :height, :color
+
+  def initialize
+    @width = 100
+    @height = 100
+    @color = :black
+    yield(self) if block_given?
+  end
+
+  def draw_rect(x, y, width, height)
+    # draws a rectangle
+  end
+
+  def to_s
+    "#{@width}x#{@height} #{@color} canvas"
+  end
+end
+
+canvas = Canvas.new do |c|
+ c.width = 800
+ c.height = 600
+ c.color = :green
+end
+
+puts canvas